Applications that need to define a subclass of InputStream
* must always provide a method that returns the next byte of input.
*
* @author Arthur van Hoff
* @see java.io.BufferedInputStream
* @see java.io.ByteArrayInputStream
* @see java.io.DataInputStream
* @see java.io.FilterInputStream
* @see java.io.InputStream#read()
* @see java.io.OutputStream
* @see java.io.PushbackInputStream
* @since 1.0
*/
public abstract class InputStream implements Closeable {
// MAX_SKIP_BUFFER_SIZE is used to determine the maximum buffer size to
// use when skipping.
private static final int MAX_SKIP_BUFFER_SIZE = 2048;
private static final int DEFAULT_BUFFER_SIZE = 8192;
/**
* Returns a new {@code InputStream} that reads no bytes. The returned
* stream is initially open. The stream is closed by calling the
* {@code close()} method. Subsequent calls to {@code close()} have no
* effect.
*
*
While the stream is open, the {@code available()}, {@code read()}, * {@code read(byte[])}, {@code read(byte[], int, int)}, * {@code readAllBytes()}, {@code readNBytes(byte[], int, int)}, * {@code readNBytes(int)}, {@code skip(long)}, and * {@code transferTo()} methods all behave as if end of stream has been * reached. After the stream has been closed, these methods all throw * {@code IOException}. * *
The {@code markSupported()} method returns {@code false}. The
* {@code mark()} method does nothing, and the {@code reset()} method
* throws {@code IOException}.
*
* @return an {@code InputStream} which contains no bytes
*
* @since 11
*/
public static InputStream nullInputStream() {
return new InputStream() {
private volatile boolean closed;
private void ensureOpen() throws IOException {
if (closed) {
throw new IOException("Stream closed");
}
}
@Override
public int available () throws IOException {
ensureOpen();
return 0;
}
@Override
public int read() throws IOException {
ensureOpen();
return -1;
}
@Override
public int read(byte[] b, int off, int len) throws IOException {
Objects.checkFromIndexSize(off, len, b.length);
if (len == 0) {
return 0;
}
ensureOpen();
return -1;
}
@Override
public byte[] readAllBytes() throws IOException {
ensureOpen();
return new byte[0];
}
@Override
public int readNBytes(byte[] b, int off, int len)
throws IOException {
Objects.checkFromIndexSize(off, len, b.length);
ensureOpen();
return 0;
}
@Override
public byte[] readNBytes(int len) throws IOException {
if (len < 0) {
throw new IllegalArgumentException("len < 0");
}
ensureOpen();
return new byte[0];
}
@Override
public long skip(long n) throws IOException {
ensureOpen();
return 0L;
}
@Override
public long transferTo(OutputStream out) throws IOException {
Objects.requireNonNull(out);
ensureOpen();
return 0L;
}
@Override
public void close() throws IOException {
closed = true;
}
};
}
/**
* Reads the next byte of data from the input stream. The value byte is
* returned as an int in the range 0 to
* 255. If no byte is available because the end of the stream
* has been reached, the value -1 is returned. This method
* blocks until input data is available, the end of the stream is detected,
* or an exception is thrown.
*
*
A subclass must provide an implementation of this method.
*
* @return the next byte of data, or -1 if the end of the
* stream is reached.
* @exception IOException if an I/O error occurs.
*/
public abstract int read() throws IOException;
/**
* Reads some number of bytes from the input stream and stores them into
* the buffer array b. The number of bytes actually read is
* returned as an integer. This method blocks until input data is
* available, end of file is detected, or an exception is thrown.
*
*
If the length of b is zero, then no bytes are read and
* 0 is returned; otherwise, there is an attempt to read at
* least one byte. If no byte is available because the stream is at the
* end of the file, the value -1 is returned; otherwise, at
* least one byte is read and stored into b.
*
*
The first byte read is stored into element b[0], the
* next one into b[1], and so on. The number of bytes read is,
* at most, equal to the length of b. Let k be the
* number of bytes actually read; these bytes will be stored in elements
* b[0] through b[k-1],
* leaving elements b[k] through
* b[b.length-1] unaffected.
*
*
The read(b) method for class InputStream
* has the same effect as:
read(b, 0, b.length) -1 if there is no more data because the end of
* the stream has been reached.
* @exception IOException If the first byte cannot be read for any reason
* other than the end of the file, if the input stream has been closed, or
* if some other I/O error occurs.
* @exception NullPointerException if b is null.
* @see java.io.InputStream#read(byte[], int, int)
*/
public int read(byte b[]) throws IOException {
return read(b, 0, b.length);
}
/**
* Reads up to len bytes of data from the input stream into
* an array of bytes. An attempt is made to read as many as
* len bytes, but a smaller number may be read.
* The number of bytes actually read is returned as an integer.
*
* This method blocks until input data is available, end of file is * detected, or an exception is thrown. * *
If len is zero, then no bytes are read and
* 0 is returned; otherwise, there is an attempt to read at
* least one byte. If no byte is available because the stream is at end of
* file, the value -1 is returned; otherwise, at least one
* byte is read and stored into b.
*
*
The first byte read is stored into element b[off], the
* next one into b[off+1], and so on. The number of bytes read
* is, at most, equal to len. Let k be the number of
* bytes actually read; these bytes will be stored in elements
* b[off] through b[off+k-1],
* leaving elements b[off+k] through
* b[off+len-1] unaffected.
*
*
In every case, elements b[0] through
* b[off] and elements b[off+len] through
* b[b.length-1] are unaffected.
*
*
The read(b, off, len) method
* for class InputStream simply calls the method
* read() repeatedly. If the first such call results in an
* IOException, that exception is returned from the call to
* the read(b, off, len) method. If
* any subsequent call to read() results in a
* IOException, the exception is caught and treated as if it
* were end of file; the bytes read up to that point are stored into
* b and the number of bytes read before the exception
* occurred is returned. The default implementation of this method blocks
* until the requested amount of input data len has been read,
* end of file is detected, or an exception is thrown. Subclasses are
* encouraged to provide a more efficient implementation of this method.
*
* @param b the buffer into which the data is read.
* @param off the start offset in array b
* at which the data is written.
* @param len the maximum number of bytes to read.
* @return the total number of bytes read into the buffer, or
* -1 if there is no more data because the end of
* the stream has been reached.
* @exception IOException If the first byte cannot be read for any reason
* other than end of file, or if the input stream has been closed, or if
* some other I/O error occurs.
* @exception NullPointerException If b is null.
* @exception IndexOutOfBoundsException If off is negative,
* len is negative, or len is greater than
* b.length - off
* @see java.io.InputStream#read()
*/
public int read(byte b[], int off, int len) throws IOException {
Objects.checkFromIndexSize(off, len, b.length);
if (len == 0) {
return 0;
}
int c = read();
if (c == -1) {
return -1;
}
b[off] = (byte)c;
int i = 1;
try {
for (; i < len ; i++) {
c = read();
if (c == -1) {
break;
}
b[off + i] = (byte)c;
}
} catch (IOException ee) {
}
return i;
}
/**
* The maximum size of array to allocate.
* Some VMs reserve some header words in an array.
* Attempts to allocate larger arrays may result in
* OutOfMemoryError: Requested array size exceeds VM limit
*/
private static final int MAX_BUFFER_SIZE = Integer.MAX_VALUE - 8;
/**
* Reads all remaining bytes from the input stream. This method blocks until
* all remaining bytes have been read and end of stream is detected, or an
* exception is thrown. This method does not close the input stream.
*
*
When this stream reaches end of stream, further invocations of this * method will return an empty byte array. * *
Note that this method is intended for simple cases where it is * convenient to read all bytes into a byte array. It is not intended for * reading input streams with large amounts of data. * *
The behavior for the case where the input stream is asynchronously * closed, or the thread interrupted during the read, is highly input * stream specific, and therefore not specified. * *
If an I/O error occurs reading from the input stream, then it may do * so after some, but not all, bytes have been read. Consequently the input * stream may not be at end of stream and may be in an inconsistent state. * It is strongly recommended that the stream be promptly closed if an I/O * error occurs. * * @implSpec * This method invokes {@link #readNBytes(int)} with a length of * {@link Integer#MAX_VALUE}. * * @return a byte array containing the bytes read from this input stream * @throws IOException if an I/O error occurs * @throws OutOfMemoryError if an array of the required size cannot be * allocated. * * @since 9 */ public byte[] readAllBytes() throws IOException { return readNBytes(Integer.MAX_VALUE); } /** * Reads up to a specified number of bytes from the input stream. This * method blocks until the requested number of bytes have been read, end * of stream is detected, or an exception is thrown. This method does not * close the input stream. * *
The length of the returned array equals the number of bytes read * from the stream. If {@code len} is zero, then no bytes are read and * an empty byte array is returned. Otherwise, up to {@code len} bytes * are read from the stream. Fewer than {@code len} bytes may be read if * end of stream is encountered. * *
When this stream reaches end of stream, further invocations of this * method will return an empty byte array. * *
Note that this method is intended for simple cases where it is * convenient to read the specified number of bytes into a byte array. The * total amount of memory allocated by this method is proportional to the * number of bytes read from the stream which is bounded by {@code len}. * Therefore, the method may be safely called with very large values of * {@code len} provided sufficient memory is available. * *
The behavior for the case where the input stream is asynchronously * closed, or the thread interrupted during the read, is highly input * stream specific, and therefore not specified. * *
If an I/O error occurs reading from the input stream, then it may do
* so after some, but not all, bytes have been read. Consequently the input
* stream may not be at end of stream and may be in an inconsistent state.
* It is strongly recommended that the stream be promptly closed if an I/O
* error occurs.
*
* @implNote
* The number of bytes allocated to read data from this stream and return
* the result is bounded by {@code 2*(long)len}, inclusive.
*
* @param len the maximum number of bytes to read
* @return a byte array containing the bytes read from this input stream
* @throws IllegalArgumentException if {@code length} is negative
* @throws IOException if an I/O error occurs
* @throws OutOfMemoryError if an array of the required size cannot be
* allocated.
*
* @since 11
*/
public byte[] readNBytes(int len) throws IOException {
if (len < 0) {
throw new IllegalArgumentException("len < 0");
}
List In the case where end of stream is reached before {@code len} bytes
* have been read, then the actual number of bytes read will be returned.
* When this stream reaches end of stream, further invocations of this
* method will return zero.
*
* If {@code len} is zero, then no bytes are read and {@code 0} is
* returned; otherwise, there is an attempt to read up to {@code len} bytes.
*
* The first byte read is stored into element {@code b[off]}, the next
* one in to {@code b[off+1]}, and so on. The number of bytes read is, at
* most, equal to {@code len}. Let k be the number of bytes actually
* read; these bytes will be stored in elements {@code b[off]} through
* {@code b[off+}k{@code -1]}, leaving elements {@code b[off+}k
* {@code ]} through {@code b[off+len-1]} unaffected.
*
* The behavior for the case where the input stream is asynchronously
* closed, or the thread interrupted during the read, is highly input
* stream specific, and therefore not specified.
*
* If an I/O error occurs reading from the input stream, then it may do
* so after some, but not all, bytes of {@code b} have been updated with
* data from the input stream. Consequently the input stream and {@code b}
* may be in an inconsistent state. It is strongly recommended that the
* stream be promptly closed if an I/O error occurs.
*
* @param b the byte array into which the data is read
* @param off the start offset in {@code b} at which the data is written
* @param len the maximum number of bytes to read
* @return the actual number of bytes read into the buffer
* @throws IOException if an I/O error occurs
* @throws NullPointerException if {@code b} is {@code null}
* @throws IndexOutOfBoundsException If {@code off} is negative, {@code len}
* is negative, or {@code len} is greater than {@code b.length - off}
*
* @since 9
*/
public int readNBytes(byte[] b, int off, int len) throws IOException {
Objects.checkFromIndexSize(off, len, b.length);
int n = 0;
while (n < len) {
int count = read(b, off + n, len - n);
if (count < 0)
break;
n += count;
}
return n;
}
/**
* Skips over and discards The Note that while some implementations of {@code InputStream} will return
* the total number of bytes in the stream, many will not. It is
* never correct to use the return value of this method to allocate
* a buffer intended to hold all data in this stream.
*
* A subclass' implementation of this method may choose to throw an
* {@link IOException} if this input stream has been closed by
* invoking the {@link #close()} method.
*
* The {@code available} method for class {@code InputStream} always
* returns {@code 0}.
*
* This method should be overridden by subclasses.
*
* @return an estimate of the number of bytes that can be read (or skipped
* over) from this input stream without blocking or {@code 0} when
* it reaches the end of the input stream.
* @exception IOException if an I/O error occurs.
*/
public int available() throws IOException {
return 0;
}
/**
* Closes this input stream and releases any system resources associated
* with the stream.
*
* The The The general contract of Marking a closed stream should not have any effect on the stream.
*
* The The general contract of The method
* This method may block indefinitely reading from the input stream, or
* writing to the output stream. The behavior for the case where the input
* and/or output stream is asynchronously closed, or the thread
* interrupted during the transfer, is highly input and output stream
* specific, and therefore not specified.
*
* If an I/O error occurs reading from the input stream or writing to the
* output stream, then it may do so after some bytes have been read or
* written. Consequently the input stream may not be at end of stream and
* one, or both, streams may be in an inconsistent state. It is strongly
* recommended that both streams be promptly closed if an I/O error occurs.
*
* @param out the output stream, non-null
* @return the number of bytes transferred
* @throws IOException if an I/O error occurs when reading or writing
* @throws NullPointerException if {@code out} is {@code null}
*
* @since 9
*/
public long transferTo(OutputStream out) throws IOException {
Objects.requireNonNull(out, "out");
long transferred = 0;
byte[] buffer = new byte[DEFAULT_BUFFER_SIZE];
int read;
while ((read = this.read(buffer, 0, DEFAULT_BUFFER_SIZE)) >= 0) {
out.write(buffer, 0, read);
transferred += read;
}
return transferred;
}
}
n bytes of data from this input
* stream. The skip method may, for a variety of reasons, end
* up skipping over some smaller number of bytes, possibly 0.
* This may result from any of a number of conditions; reaching end of file
* before n bytes have been skipped is only one possibility.
* The actual number of bytes skipped is returned. If {@code n} is
* negative, the {@code skip} method for class {@code InputStream} always
* returns 0, and no bytes are skipped. Subclasses may handle the negative
* value differently.
*
* skip method implementation of this class creates a
* byte array and then repeatedly reads into it until n bytes
* have been read or the end of the stream has been reached. Subclasses are
* encouraged to provide a more efficient implementation of this method.
* For instance, the implementation may depend on the ability to seek.
*
* @param n the number of bytes to be skipped.
* @return the actual number of bytes skipped.
* @throws IOException if an I/O error occurs.
*/
public long skip(long n) throws IOException {
long remaining = n;
int nr;
if (n <= 0) {
return 0;
}
int size = (int)Math.min(MAX_SKIP_BUFFER_SIZE, remaining);
byte[] skipBuffer = new byte[size];
while (remaining > 0) {
nr = read(skipBuffer, 0, (int)Math.min(size, remaining));
if (nr < 0) {
break;
}
remaining -= nr;
}
return n - remaining;
}
/**
* Returns an estimate of the number of bytes that can be read (or
* skipped over) from this input stream without blocking by the next
* invocation of a method for this input stream. The next invocation
* might be the same thread or another thread. A single read or skip of this
* many bytes will not block, but may read or skip fewer bytes.
*
* close method of InputStream does
* nothing.
*
* @exception IOException if an I/O error occurs.
*/
public void close() throws IOException {}
/**
* Marks the current position in this input stream. A subsequent call to
* the reset method repositions this stream at the last marked
* position so that subsequent reads re-read the same bytes.
*
* readlimit arguments tells this input stream to
* allow that many bytes to be read before the mark position gets
* invalidated.
*
* mark is that, if the method
* markSupported returns true, the stream somehow
* remembers all the bytes read after the call to mark and
* stands ready to supply those same bytes again if and whenever the method
* reset is called. However, the stream is not required to
* remember any data at all if more than readlimit bytes are
* read from the stream before reset is called.
*
* mark method of InputStream does
* nothing.
*
* @param readlimit the maximum limit of bytes that can be read before
* the mark position becomes invalid.
* @see java.io.InputStream#reset()
*/
public synchronized void mark(int readlimit) {}
/**
* Repositions this stream to the position at the time the
* mark method was last called on this input stream.
*
* reset is:
*
*
*
*
* markSupported returns
* true, then:
*
*
*
* mark has not been called since
* the stream was created, or the number of bytes read from the stream
* since mark was last called is larger than the argument
* to mark at that last call, then an
* IOException might be thrown.
*
* IOException is not thrown, then the
* stream is reset to a state such that all the bytes read since the
* most recent call to mark (or since the start of the
* file, if mark has not been called) will be resupplied
* to subsequent callers of the read method, followed by
* any bytes that otherwise would have been the next input data as of
* the time of the call to reset. markSupported returns
* false, then:
*
* reset may throw an
* IOException.
*
* IOException is not thrown, then the stream
* is reset to a fixed state that depends on the particular type of the
* input stream and how it was created. The bytes that will be supplied
* to subsequent callers of the read method depend on the
* particular type of the input stream. reset for class InputStream
* does nothing except throw an IOException.
*
* @exception IOException if this stream has not been marked or if the
* mark has been invalidated.
* @see java.io.InputStream#mark(int)
* @see java.io.IOException
*/
public synchronized void reset() throws IOException {
throw new IOException("mark/reset not supported");
}
/**
* Tests if this input stream supports the mark and
* reset methods. Whether or not mark and
* reset are supported is an invariant property of a
* particular input stream instance. The markSupported method
* of InputStream returns false.
*
* @return true if this stream instance supports the mark
* and reset methods; false otherwise.
* @see java.io.InputStream#mark(int)
* @see java.io.InputStream#reset()
*/
public boolean markSupported() {
return false;
}
/**
* Reads all bytes from this input stream and writes the bytes to the
* given output stream in the order that they are read. On return, this
* input stream will be at end of stream. This method does not close either
* stream.
*